ABSTRACT
All model intercomparison projects (MIPs) have shown large uncertainties in prediction of carbon sequestration among models and poor model-data matches. Although great efforts have been made, it is still difficult to identify causes of model uncertainty. This chapter offers a unified diagnostic system, which is also called a 1-3-5 scheme of diagnostics, for uncertainty analysis in carbon cycle modeling. The number 1 stands for one formula to unify the land carbon models, the number 3 is for one three-dimensional (3D) space to evaluate all model outputs, and the number 5 is for five traceable components to pinpoint uncertainty sources via traceability analysis. Once the uncertainty sources are pinpointed, the model uncertainty can be shrunk to zero by standardizing the traceable components.
